| Ion-Selective Electrode Meter | Uses an ion-selective membrane that develops a potential related to the activity of a target ion. The meter converts this electrical signal into concentration after calibration. | Fluoride, chloride, nitrate, ammonium, calcium, potassium, sodium, hydrogen ions, and other selected ions. | Often from low milligram-per-liter levels to grams per liter, depending on the electrode, sample matrix, and calibration method. | Portable options are available; direct measurements can be relatively fast; suitable for field and laboratory testing. | Requires correct calibration, conditioning, temperature control, and maintenance. Interfering ions and high ionic strength can affect results. |
| pH Meter | Measures the potential difference between a glass electrode and a reference electrode. The signal is related to hydrogen-ion activity and is displayed as pH. | Hydrogen ions in aqueous solutions. | Commonly pH 0 to 14, although specialized electrodes may cover a narrower or wider usable range. | Fast, widely used, and useful for water treatment, laboratories, agriculture, food processing, and environmental testing. | The electrode must remain properly hydrated and clean. Temperature and sample composition influence the reading. |
| Ion Test Strip | A chemical reagent on the strip reacts with a target ion and changes color. The color is compared with a printed reference scale or read by an optical device. | Nitrate, nitrite, chloride, hardness-related ions, ammonium, phosphate, and other test-specific analytes. | Usually designed for screening ranges, commonly from low parts-per-million levels to several hundred or thousand milligrams per liter. | Low cost, lightweight, simple to use, and requires little equipment or training. | Visual color matching is less precise than instrumental analysis. Shelf life, lighting, timing, and sample color can affect results. |
| Colorimetric Ion Tester | A reagent forms a colored compound with the target ion. The instrument measures absorbance or color intensity and calculates concentration using a calibration relationship. | Ammonium, phosphate, iron, copper, nitrate, residual chlorine, and other reagent-compatible analytes. | Commonly covers low microgram-per-liter to milligram-per-liter concentrations, depending on the chemistry and optical path. | More objective and often more sensitive than visual test strips; useful for routine water analysis. | Reagents have expiration dates. Turbidity, sample color, reaction time, and incorrect dosing can cause errors. |
| Ion Chromatograph | Separates ions in a chromatography column and detects them, commonly through conductivity after suppression or through another selective detector. | Fluoride, chloride, bromide, nitrate, sulfate, phosphate, lithium, sodium, ammonium, potassium, magnesium, and calcium. | Frequently used from low microgram-per-liter levels to tens or hundreds of milligrams per liter, depending on the method and dilution. | Can identify and quantify multiple ions in one run with strong selectivity and sensitivity. | Higher purchase and operating cost; requires trained operators, controlled methods, clean eluent, and regular maintenance. |
| Conductivity or TDS Tester | Applies an electrical signal between electrodes and measures how readily the solution conducts electricity. TDS is estimated from conductivity using a conversion factor. | Total dissolved ionic material rather than a specific ion; temperature-compensated conductivity and estimated total dissolved solids. | Conductivity may span approximately 0.05 microsiemens per centimeter to hundreds of millisiemens per centimeter, depending on the instrument. | Very fast and convenient for checking water purity, rinsing quality, and changes in dissolved ionic content. | Cannot identify individual ions. TDS values are estimates and depend on the selected conversion factor and solution composition. |
| Static Ion Balance Tester | Measures electrostatic voltage, decay time, or ion balance near a surface. Some models use an internal sensor or a controlled ion source to evaluate charge neutralization. | Positive and negative air ions, surface voltage, charge decay, and ionizer balance. | Voltage ranges commonly extend from a few volts to several kilovolts; ion balance is often reported in volts and decay in seconds. | Useful for evaluating electrostatic discharge risks in electronics manufacturing, cleanrooms, and material-handling areas. | Readings depend strongly on distance, airflow, humidity, grounding, and measurement geometry. It does not measure dissolved ions in water. |